1. Field of the Invention
This invention pertains generally to equipment for charging electrical power storage devices, and more particularly to an apparatus and method for monitoring the state of a contactor which connects the power charging source with the electrical power storage device load.
2. Description of the Background Art
Contactors are used for connecting or switching high current loads, such as may be found in the connection of an electric vehicle to a charging device. A large capacity electrical power storage device, such as a battery, typically requires a high current charging system so that the device may be charged within a reasonable period of time. When charging these large loads, the point of interface between the charging system and the device to be charged is called a contactor. The contactor provides a conduction path via "contacts" between the charger and the battery through which charging current flows. If the contactor becomes dirty, or contaminated, the resistance of the conduction path increases. At high currents, such as used when charging the power storage device in an electric vehicle, even small increases in resistance in the contactor can dissipate large amounts of energy and, in so doing, generate huge amounts of heat. The heat that is generated can be localized, wherein pitting, corrosion, or other damage to the contactor may occur thereby rendering it inoperative or unsafe. Therefore, when charging large capacity electrical power storage devices it is desirable to monitor the state of the contactor.